WASHINGTON (AP)  Many more low- and moderate-income working families are spending at least half their salaries on rent or mortgages, according to a study released Tuesday by affordable housing advocates.

More than 4 million households fell into that category last year, a 67 percent increase in four years. The surge is due to increases in housing prices outstripping wages, said the Center for Housing Policy and its parent organization, the National Housing Conference. The result is many people must cut spending elsewhere, such as retirement savings, researchers said.

Pedro Aguilar, 37, his wife and their two teenage daughters moved from San Francisco two years ago because housing prices had become unaffordable. They moved to Antioch, Calif., about an hour away, but now find themselves again struggling to pay the rent.

Aguilar, a janitor, and his wife make about $3,000 a month. They pay $1,500-a-month for a three-bedroom apartment, but their rent is set to increase by $300 next month. Aguilar said his yearly raises of 40 cents an hour don't cover the rising housing costs.

``A long time ago, when I was in Mexico, I thought I could make enough money to live better in the United States. Now, I don't know,'' Aguilar said.

The study identified low- to moderate-income families as those who worked the equivalent of a full-time job and earned between the minimum wage of $10,712 and 120 percent of the median income in their area.

The report dispels the notion that the housing crunch is most severe for renters and for the working poor in cities, researchers said.

Some 61 percent of working people who spend more than half their salaries on housing live outside cities, the study found.

And between 1999 and 2001, the number of homeowners who spent more than half their income on housing rose 36 percent, outpacing the 24 percent rise among renters.

Ann Schnare, president of the Center for Housing Policy, said part of the problem stems from the slowing economy. But ``a lot of the problem is also asking the question of how we can create conditions in this country to create affordable housing.''

Among the ways, her group suggests, are more money to fund or leverage the money necessary to produce more affordable housing, or preserve the existing affordable housing supply.

Ron Utt, a senior researcher at the conservative Heritage Foundation, said the study failed to consider that some people may have paid too much for a home or apartment. ``Are we supposed to start feeling sorry for someone making $70,000 a year and overbought?'' he asked.

He acknowledged that housing prices have risen far faster than income in some places, but said the study still overstates the problem.

``You are coming off the best years of home sales and home ownership is at an all-time high (of 69 percent),'' he said.

Jared Bernstein, an economist at the Economic Policy Institute, a think-tank, said if the economy continues to falter while housing prices remain high, more people will have to devote greater portions of their income to rents and mortgages.

``If families couldn't keep pace with housing costs even in the best of times, this problem will only get worse unless we find a way out of this jobless recovery,'' Bernstein said.

The study found there were nearly 14.4 million low- and moderate-income families, regardless of working status, with critical housing needs, including retirees and those who make less than minimum wage. That figure was up from 13.1 million in 1999.

Most of that increase  nearly 1 million  came among families who worked the equivalent of a full-time job.